JPH05237693A - Self-shielded arc welding flux cored wire for all-position welding - Google Patents

Abstract

PURPOSE:To provide the flux cored wire for self-shielded arc welding which can yield a weld metal having various excellent mechanical performance (more particularly toughness) without weld defects, such as pits and lack of fusion, in all welding positions by specifying the component compsn. of the flux to be filled in a steel sheath. CONSTITUTION:This self-shielded arc welding flux cored wire for all position welding is constituted by filling the particulate flux contg. the following components as essential components at 15 to 30% (weight %, hereafter the same) of the total wire of the wire into the steel sheath: The compsn. consists of 32 to 70% BaF2, 1 to 30% fluoride of an alkaline metal, 1 to 30% multi component oxide consisting of the oxide of alkaline earth metals selected from a group consisting of Ca, Sr and Ba and the oxide of metals selected from a group consisting of Fe, Mn, Ni, Co, Ti, Al, Zr, 3 to 12% Al, 2 to 10% Mg, 0.5 to 10% Mn, 0.5 to 20% Ni and 0.1 to 4% Zr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux-cored wire for self-shielding arc welding, and more particularly to a flux-cored wire which is free from welding defects such as pits and fusion defects and which has a high toughness and can be obtained by all-position welding. It is a thing.

[0002]

_2. Description of the Related Art A flux-cored wire is a metal sheath filled with flux, and the general composition of the flux used here is CaF ₂ as a slag forming agent or a shielding agent, a deoxidizing / denitrifying agent. As a main component, and Mg as a deoxidizing / shielding agent as a main component. When this flux-cored wire is used, it is not necessary to separately supply a shielding gas or flux, so that it has various advantages such as good welding workability and excellent wind resistance.

[0003]

However, at present, its use is limited to a specific field of outdoor welding in civil engineering, construction, etc., and it cannot be said that it is fully utilized. The following drawbacks can be cited as reasons why the application is limited and the spread to other fields is delayed. High melting point MgO and A derived from Al added as deoxidizing / denitrifying agent and Mg added as deoxidizing / shielding agent
Since l ₂ O ₃ is the main component of the produced slag, slag entrainment is likely to occur especially when applied to multilayer welding. In addition to a large amount of Al retained in the deposited metal, abnormal reduction of oxygen (about 50 to 100 ppm) tends to cause coarsening of crystal grains, and good notch toughness cannot be obtained. Since the surface tensions of the generated slag and the molten metal are too large, the beads are likely to droop in the upright posture and the upward posture. The proper arc voltage range is narrow, and pits and blow holes cannot be eliminated unless the voltage and wire protrusion length are strictly controlled. Mg and CaF with high vapor pressure as the filling flux component
Since a large amount of ₂ is used, the amount of fumes generated is large and the working environment is significantly impaired.

[0004]

[Means for Solving the Problems] The inventors of the present invention have eagerly studied to solve the above-mentioned drawbacks of the flux-cored wire and to make it possible to widely utilize the excellent wind resistance, which is the greatest feature of the flux-cored wire. It was The present invention has been completed as a result of these studies, and its constitution is a powdery and granular flux containing the following components as essential components in a steel sheath,
The gist is that the wire is filled in an amount of 15 to 30% (weight%: the same hereinafter) with respect to the total weight of the wire. BaF _2: 32 to 70% alkali metal fluoride: 30% Ca, and oxides of alkaline earth metal selected from the group consisting of Sr and Ba, Fe, Mn, Ni, Co, Ti,
Composite oxide with oxide of metal selected from the group consisting of Al and Zr: 1 to 30% Al: 3 to 12% Mg: 2 to 10% Mn: 0.5 to 10% Ni: 0.5 to 20% Zr: 0.1-4%

[0005]

The reason why the components contained in the powdery and granular flux are determined in the present invention will be described in detail below. First, 32 to 70% of BaF ₂ is added as the main slag forming component. That is, B
aF ₂ is C which is commonly used as a slag former.
Compared to aF ₂ and SrF _2, it has better droplet transfer and shielding properties, and also has the effect of suppressing the drooling of the molten metal in the upright posture. These characteristics are particularly remarkable in the case of DC positive polarity. To be demonstrated. 32% of BaF ₂
If less than 70%, these characteristics are not effectively exhibited, while 70%
If it exceeds the range, the amount of slag produced becomes excessive, welding defects such as slag inclusion are likely to occur, and the welding workability also deteriorates.

By the way, BaF ₂ has the following drawbacks in view of its performance as a slag forming agent. That is Ba
F ₂ has a property of making the penetration shallower than conventional CaF ₂ and SrF ₂ , and moreover, Al ₂ O ₃ which is a reaction product of Al and Mg added as a deoxidizing agent / denitrifying agent described later. Since a slag with a high melting point is formed together with MgO and MgO, welding defects such as slag entrainment and fusion failure are likely to occur, and the gloss and appearance of the beads cannot be said to be good. Such BaF ₂
In order to improve the above-mentioned drawback, in the present invention, an appropriate amount of alkali metal fluoride and a composite oxide of an alkaline earth metal oxide and a metal oxide described later are used in combination.

First, the alkali metal (Li, K, Na, etc.) fluoride adjusts the melting point and viscosity of the produced slag, strengthens and stabilizes the arc force to deepen the penetration, and causes slag inclusion and fusion failure. Fulfills the function of suppressing defects.
In order to secure such a function, the content must be 1% or more, but if it exceeds 30%, the fluidity of the slag becomes excessive, the encapsulation property deteriorates, and the bead appearance deteriorates.
The slag abnormally strongly adheres and the releasability deteriorates, and further, the slag and the molten metal droop down significantly in the upright position and the upright position. Since the water content in the flux causes the generation of pores in the weld metal, Na ₂ ZrF ₆ , K ₂ SiF ₆ , and K ₂ Z, which are hardly hygroscopic as an alkali metal fluoride, are used.
rF ₆ , LiF, LiBaF ₃ etc. are most suitable.

Next, an alkaline earth metal oxide selected from the group consisting of Ca, Sr and Ba, and Fe, Mn, N
A composite oxide with an oxide of a metal selected from the group consisting of i, Co, Ti, Al and Zr improves the appearance and gloss of beads and enhances the slag shield effect, and
Oxygen is added to the weld metal excessively deoxidized by a strong deoxidizer such as Mg or Mg to enhance notch toughness. In order to effectively exhibit these functions, 1% of the above composite oxide is used.
The above must be contained. However, if it exceeds 30%, the droplets become large and spatter frequently occurs, and the slag removability deteriorates.

By the way, the above-mentioned alkaline earth metal oxide easily absorbs moisture in the air and absorbs CO ₂ and has a high melting point. Therefore, when it is used alone, welding defects such as pores and slag inclusion are likely to occur. Also, spatter frequently occurs. However, when a complex oxide is formed between this and the above-mentioned metal oxide, it becomes a hardly hygroscopic and stable compound, and Fe, Mn
The composite oxide with the above oxide has a lower melting point than the alkaline earth metal oxide alone. These complex oxides are M _x N _y
The general formula of O _z (wherein M is Ca, Sr, or Ba,
N can be represented by any of Fe, Mn, Ni, Co, Ti, Al, and Zr, and x, y, and z are positive numbers. For example, CaFe is a composite oxide in which M is Ca.
₂ O ₄ , Ca ₂ FeO ₅ , Ca ₂ MnO ₄ , CaMn ₂
O ₄ , CaMn ₃ O _10, etc. are Sr ₂ FeO ₄ , Sr ₇ Fe ₁₀ O ₂₂ , SrFe as complex oxides in which M is Sr.
O _2.5 , Sr ₂ Fe ₂ O ₅ , Sr ₃ SiO ₅ , SrSi
O ₃ , SrMnO ₃ , Sr ₂ MnO ₄ , Sr ₃ Mn ₂ O ₇
, SrNiO ₃ , SrTiO ₃ , Sr ₃ Al ₂ O ₆ ,
Sr ₂ ZrO _4, etc., and BaFe ₂ O ₄ , Ba (MnO ₄ ) ₂ , Ba ₃ Ni as complex oxides in which M is Ba.
O ₄ , BaSiO ₄ , BaSiO ₃ , Ba ₃ SiO _{4 and the} like are illustrated as typical examples. However, Si
Is a strong deoxidizer for Al and Mg.
It is not included as an essential element of the present invention because it is reduced by the above method and remains in the deposited metal as Si, and the ferrite crystal structure is coarsened to lower the toughness.

Al is an indispensable element as a strong deoxidizing agent and denitrifying agent and as a nitrogen fixing agent, and traps oxygen and nitrogen invading from the atmosphere to prevent generation of pores. In order to exert such an effect of Al, it is necessary to contain 3% or more in the flux, but if too much is added, an excessive amount of Al is retained in the deposited metal and the crystal grains become coarse and fragile. It should be kept below. As the Al source, Al alloys such as Fe-Al, Al-Mg, and Al-Li can be used in addition to metallic Al.

In addition to having a strong deoxidizing function, Mg easily becomes a metal vapor by arc heat and exhibits an excellent shielding effect. If the amount of Mg is less than 2%, such effects are not sufficiently exhibited, and the yield of Al used in combination decreases, and
The denitrifying effect and nitrogen fixing effect of 1 cannot be fully exerted. However, if the amount is too large, the amount of fumes increases significantly, making it difficult to observe the molten pool, contaminating the work environment, and deteriorating the encapsulation due to an increase in spatter and viscosity of the slag. Should be. Incidentally Mg
It is also possible to use metallic Mg as a source, but this tends to cause explosive vaporization due to arc heat and frequent spattering, so Al-Mg, Mg-Si, M
It is preferable to contain it as a Mg alloy such as g-Si-Ca, Ni-Mg, and Li-Mg.

Mn not only enhances the strength of the deposited metal, but also lowers the surface tension of the molten metal to adjust the bead shape, so that Mn must be contained in at least 0.5%. However, if it exceeds 10%, the strength of the deposited metal becomes excessive and ductility and crack resistance become poor. As the Mn source, metallic Mn and Mn alloys such as Fe-Mn and Fe-Si-Mn are used, but other oxides such as MnO and MnO ₂ and further Li.
Complex oxides such as ₂ MnO ₃ , SrMnO ₃ , Ba (MnO ₄ ) can also be used as the Mn source. The reason is that the flux used in the present invention contains a large amount of elements (Al and Mg) having a greater affinity for oxygen than Mn, so the Mn oxide is deoxidized and converted to metallic Mn. Because it is done.

Ni is an austenite forming element, and has an action of suppressing coarsening of flux crystal grains due to the yield of a large amount of Al and enhancing the notch toughness of the molten metal. Such an effect is effectively exhibited in a composition of 0.5% or more, but 20
If it exceeds%, the strength becomes excessive and the crack resistance becomes poor. As the Ni source, in addition to metallic Ni, Fe-Ni-Cr,
Ni alloy such as Ni-Mg, or NiO, Ba ₂ Ni
Examples thereof include oxides such as O ₄ and complex oxides.

Zr has the function of refining the crystal grains of the deposited metal and fixing the invading nitrogen to improve the notch toughness, and these effects are effectively exhibited by the addition of 0.1% or more. However, if it exceeds 4%, seizure of the slag becomes remarkable, the peelability deteriorates, and the notch toughness rather deteriorates. By the way, FIG. 1 shows BaF ₂ : 50%, LiF: 3.
5%, SrMnO ₃ : 6%, Al: 9.2%, Mg: 7
%, Mn: 0.5%, Ni: 5%, balance Fe with Zr added to Fe-Zr (Zr: 30
%) In the form of 0.1-5%,
Welding experiments were conducted using a flux-cored wire of 1.6 mmφ obtained by drawing 20% of the total weight of the wire in a mild steel sheath and wire drawing, and investigated the relationship between the Zr content in the flux and the notch toughness. It is a thing. The welding test conditions were as follows.

[Test Conditions] Base material: SM-50A, plate thickness 19 mm, welding position: downward, 7 layers 13 baths, welding current: 250 A, DC (-) welding voltage: 21 V, welding speed: 15-22 cm / min, wire protrusion length S: 25 mm Notch toughness test: 2 mm V notch Charpy test method of JIS Z3112

As is clear from FIG. 1, notch toughness is remarkably improved by incorporating Zr in the flux in an amount of 0.1 to 4%. Note The Zr source Fe-Zr, Zr-Si or the like of the alloy or K ₂ ZrF _6, fluoride such as Na ₂ ZrF ₆ or ZrO _2, ZrSiO _4, (zircon sand), Li ₂
Examples thereof include oxides such as ZrO ₃ and complex oxides.

The essential components of the flux used in the present invention are as described above, but are particularly applied to fields requiring low temperature toughness [generally (-10) to (-60) ° C] such as offshore structures. In the case of Ti: 0.01 to 0.5%,
B: It is also effective to add 0.01 to 0.2%, and to add a rare earth element such as Ce. A brief description of these sub-compounding components is given below.

Ti has an action of enhancing notch toughness with an extremely small amount, and its effect is effectively exhibited at 0.01% or more. In this case, Zr in the range described above or 0.01 to 0.2%
When used in combination with B, the effect becomes more remarkable. However, T
If the amount of i exceeds 0.5%, seizure of the slag becomes remarkable, and the bead appearance and welding efficiency deteriorate. As the Ti source, in addition to metal Ti, alloys such as Fe-Ti, TiO ₂ and T
Oxides such as i ₂ O ₃ or Li ₂ TiO ₃ , CaT
It is also possible to use a complex oxide such as i ₂ O ₄ or CaTiO ₃ .

Although B alone exhibits almost no notch toughness improving effect, it has a function of promoting the effect of Ti when used in combination with an appropriate amount of Ti as described above. Such an effect is 0.
When the content is more than 01%, it is effectively exhibited, but when it exceeds 0.2%, the quenching hardening lowers the crack resistance and the notch toughness becomes poor. As a B source, an alloy such as Fe-B or B ₂ O ₃
Oxides such as Li ₂ B ₄ O ₇ , Na ₂ B ₄ O ₇
And other complex oxides.

In addition to the above, the flux contains Al ₂ O ₃ , MgO, FeO, Fe ₂ O ₃ and Na ₂ as slag forming agents.
O, K ₂ O, LiFeO ₂ , Li ₂ MnO ₃ , Li ₂ S
Oxides such as iO ₃ , SiO ₂ and CaF ₂ , SrF ₂ , M
Fluorides such as gF ₂ , NaF, Na ₃ AlF ₆ and Na ₂ SiF ₆ , as well as Li ₂ CO ₃ , Na ₂ CO ₃ and BaC.
O ₃ , CaCO ₃ , MgCO ₃ , SrCO ₃ , MnCO
Carbonates such as ₃ can be added, and Cr, M are added to improve mechanical properties such as high temperature strength of weld metal and corrosion resistance.
Elements such as o, Cu, Nb, V, Co and P can also be blended.

The flux composition to be filled in the steel sheath has been described above, but the flux filling rate is also extremely important in order to effectively bring out the effects of these components.
The filling rate must be set so that the filling amount with respect to the total weight of the wire is in the range of 15 to 30%. That is, if the filling rate is less than 15%, a satisfactory effect cannot be obtained because the individual contents of the flux components defined above are insufficient, while if it exceeds 30%, alloys such as Al in the weld metal are not obtained. There is a problem that the amount becomes excessive and the desired mechanical properties cannot be obtained, or the amount of generated slag becomes too large, the slag is significantly involved, and the welding workability is deteriorated.

Mild steel is the most common material for the steel sheath, but low-alloy steel, high-alloy steel, etc. can be used depending on the application, and the cross-sectional structure is not particularly limited, but it is 2 mmφ or less. In the case of a small diameter, a relatively simple cylindrical shape is used, and in the case of a large diameter wire of about 2.4 to 4 mmφ, a structure in which a sheath material is complicatedly folded inside is generally used.

[0023]

EFFECTS OF THE INVENTION The present invention is configured as described above, and in particular, by specifying the composition of the flux to be filled in the steel sheath, there are no welding defects such as pits and fusion defects, and mechanical properties are eliminated. It has become possible to provide a flux-cored wire for self-shielded arc welding, which makes it possible to obtain a weld metal having excellent properties (particularly toughness) in all welding positions. Next, the effects of the present invention will be clarified with reference to examples.

[0024]

【Example】

Example 1 A steel sheath having the chemical composition shown in Table 1 was filled with a powdery granular flux having the composition shown in Table 2 (filling rate 20%), and wire drawing was performed to produce a 2 mmφ flux-cored wire. A welding experiment was conducted using the obtained wire under the following conditions. The results are shown in Tables 3 and 4.

[Welding conditions] Test plate: JIS G3106, SM-50A, plate thickness 45
mm x length 500 mm Groove shape: X groove (Fig. 2) Welding current: 250 (A), DO [wire (-)] Welding voltage: 21-22 (V) Welding speed: 13-24 (cm / min) ) Wire protrusion length: 20-25 (mm) Formation method: 8 layers 14 passes for both front and back sides Welding position: Downward Back chipping: Black skin removed with grinder after arc air gouging

[Test Method] Tensile time: JIS Z3111 Impact test: JIS Z3112 Side bending test: JIS Z3122 Ultrasonic flaw detection test: JIS Z3060

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

* 1 Tensile test piece: 1 after machining before testing
Aging treatment at 00 ° C for 24 hours * 2 Side bending test: bending angle 180 °, bending radius 19m
m * 3 Ultrasonic flaw detection test: Total number of blowholes and total length of slag winding / fusion failure. * 4 Evaluation of welding workability ◎: Excellent, ○: Good, △: Poor Welding current × Welding voltage: Downward attitude 250A × 21V Vertical attitude 170A × 20V Other welding conditions are the same as those of downward joint welding.

Examples 2 to 8 and Comparative Example A steel sheath having the chemical composition shown in Table 1 was filled with a powdery granular flux having the composition shown in Table 5 (filling rate 20%), and wire drawing was carried out. A flux-cored wire having a diameter of 0.6 mm was manufactured. A welding experiment was conducted using the obtained wire under the following conditions. The results are shown in Table 6. [Welding conditions] Base material: SM-50A, plate thickness 19 mm Welding position: downward, 7 layers 13 baths Welding current: 250 A, DC (-) Welding voltage: 21 V Welding speed: 15-22 cm / min Wire protrusion length: 25 mm Notch toughness test: JIS Z3112 2 mm V notch Charpy test method

[0033]

[Table 5]

[0034]

[Table 6]

* 1 Tensile test piece: 1 after machining before testing
00 ℃ × 24 hours aging treatment * 4 Welding workability evaluation ◎: Excellent, ○: Good, △: Poor Welding current × Welding voltage: Downward posture 250A × 21V Vertical posture 170A × 20V Other welding conditions are downward Same as the conditions for joint welding.

As is clear from Tables 3, 4, and 6, when a wire (embodiment) satisfying the requirements specified in the present invention is used, the welding workability is good and blowholes, slag inclusion, and fusion are performed. There are no defects such as defects, and the mechanical properties of the deposited metal are good. Above all, appropriate amount of Ti and Zr in the flux
The low temperature (−30 ° C.) notch toughness of the deposited metal obtained by using the wire (Example 1) in which the above was compounded is extremely excellent. On the other hand, when the comparative wire lacking the requirements of the present invention is used, the welding workability and mechanical properties are poor, and the object of the present invention cannot be achieved.

[Brief description of drawings]

FIG. 1 is an experimental graph showing the relationship between the amount of Zr in flux and the impact value.

FIG. 2 is a view showing a groove shape adopted in a welding experiment.

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[Procedure amendment]

[Submission date] May 18, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

[Means for Solving the Problems] The inventors of the present invention have eagerly studied to solve the above-mentioned drawbacks of the flux-cored wire and to make it possible to widely utilize the excellent wind resistance, which is the greatest feature of the flux-cored wire. It was The present invention has been completed as a result of these studies, and its constitution is a powdery and granular flux containing the following components as essential components in a steel sheath,
The gist is that the wire is filled in an amount of 15 to 30% (weight%: the same hereinafter) with respect to the total weight of the wire. BaF _2: 32 to 70% alkali metal fluoride: an oxide of 1 to 30% Ca, alkaline earth metal selected from the group consisting of Sr and Ba, Fe, Mn, Ni, Co, Ti,
Composite oxide with oxide of metal selected from the group consisting of Al and Zr: 1 to 30% Al: 3 to 12% Mg: 2 to 10% Mn: 0.5 to 10% Ni: 0.5 to 20% Zr: 0.1-4%

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

As is clear from FIG. 1, notch toughness is remarkably improved by incorporating Zr in the flux in an amount of 0.1 to 4%. Examples of the Zr source include alloys such as Fe-Zr and Zr-Si.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction content]

[0033]

[Table 5]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

[0034]

[Table 6]

Claims (1)

[Claims] 1. A self-positioning tool for all-position welding, characterized in that a steel sheath is filled with 15 to 30% by weight of a powdery or granular flux containing the following components as essential components with respect to the total weight of the wire. Shield arc welding flux-cored wire. BaF ₂ : 32 to 70% by weight Alkali metal fluoride: 1 to 30% by weight Alkaline earth metal oxide selected from the group consisting of Ca, Sr and Ba, and Fe, Mn, Ni, Co, Ti,
Composite oxide with oxide of metal selected from the group consisting of Al and Zr: 1 to 30% by weight Al: 3 to 12% by weight Mg: 2 to 10% by weight Mn: 0.5 to 10% by weight Ni: 0.5 to 20% by weight Zr: 0.1 to 4% by weight